It is roughly oval in plan, measuring about 37 metres north to south and 46 metres east to west, and its enclosing bank rises only a metre above the surrounding ground. What makes it quietly peculiar is its origin: rather than being built up from scratch, the enclosure appears to have been formed around a natural rise in the terrain, the land itself providing the bones of the structure, with a modest earthen bank added to define the boundary. The interior slopes noticeably from west to east, a detail that hints at how the natural topography was incorporated rather than levelled.

This kind of earthwork enclosure, a roughly circular area defined by a bank and sometimes a ditch, is a feature of the Irish countryside that spans a very wide range of periods and purposes. Some were farmsteads, some ceremonial, some defensive. The one at Reanacaheragh does not announce which category it belongs to. What the cartographic record does show is that by 1842, when the Ordnance Survey produced its first detailed six-inch mapping of Ireland, the feature was already visible enough to be recorded as a hachured circular area, the surveyors' way of indicating a raised or mounded form. By the time the revised six-inch map was drawn in 1904, the same area appears simply as a circular field, suggesting it had been absorbed into agricultural use, its ancient outline repurposed as a field boundary without anyone necessarily thinking twice about what it was.